Biochemistry: Lipids and Biological Membranes

Comprehensive flashcards covering the classes, nomenclature, physical properties, and biological functions of lipids as discussed in the lecture notes.

Lipids

Biological compounds that are insoluble in water (hydrophobic) but soluble in organic solvents such as chloroform and methanol.

Lipid Maps

The lipid equivalent of the Protein Data Bank (PDB), serving as a database for lipid structures.

Paracrine hormones

Signaling molecules that act locally, rather than body-wide.

Antioxidants

Lipid functions exemplified by vitamin E that protect against oxidative damage.

Fatty Acids

Carboxylic acids with hydrocarbon chains containing anywhere from $4$ to $36$ carbons, usually in an even number.

Saturated Fatty Acids

Fatty acids with no double bonds between carbons in the alkyl chain.

Unsaturated Fatty Acids

Fatty acids containing one or more double bonds in the alkyl chain.

Omega ($\omega$) numbering

A nomenclature system for polyunsaturated fatty acids where the first carbon is identified in relationship to the terminal methyl carbon.

Essential Nutrients

Nutrients like $\omega-3$ and $\omega-6$ fatty acids that humans need but cannot synthesize and must obtain from their diet.

Solubility of Fatty Acids

Decreases as the chain length increases or as the number of double bonds decreases.

Melting Point of Fatty Acids

Increases with longer chain length and decreases with more double bonds.

Trans fatty acids

Fatty acids formed by partial hydrogenation of unsaturated fats that take on an extended conformation, allowing them to pack more regularly and have higher melting points.

Triacylglycerols (Triglyceride)

The primary storage form of lipids (body fat) consisting of a glycerol backbone esterified to three fatty acids.

Lipases

Enzymes that catalyze the hydrolysis of stored triacylglycerols, releasing fatty acids.

Waxes

Esters of long-chain saturated and unsaturated fatty acids with long-chain alcohols, characterized by high melting points between $60$ and $100^\circ\text{C}$.

Glycerophospholipids

Primary constituents of cell membranes with an $L$-glycerol-3-phosphate backbone.

Cardiolipin (Diphosphatidylglycerol)

A glycerophospholipid with a net charge of $-2$ at $pH\,7$, consisting of two phosphatidic acids joined by a glycerol.

Sphingolipids

Membrane lipids with a sphingosine backbone where a fatty acid is joined via an amide linkage rather than an ester linkage.

Sphingomyelin

A sphingolipid abundant in the myelin sheath that surrounds animal nerve cells.

Glycosphingolipids

Lipids that determine human blood groups based on the type of sugars located on their head groups.

Galactolipids

Phosphate-free lipids that make up $70$ to $80\%$ of membrane lipids in plants.

Phospholipases

Enzymes designated $A$ through $D$ that cleave specific bonds to degrade and replace membrane lipids.

Sterols

Structural lipids in eukaryotic membranes characterized by a steroid nucleus of four fused rings and a polar hydroxyl group at $C-3$.

Phosphatidylinositol 4,5-bisphosphate ($PIP_2$)

An intracellular signaling molecule that serves as a reservoir for messenger molecules released in response to extracellular signals.

Eicosanoids

Paracrine hormones derived from arachidonic acid ($20:4(\Delta^{5,8,11,14})$), including prostaglandins, thromboxanes, and leukotrienes.

NSAIDs

Nonsteroidal anti-inflammatory drugs like aspirin and ibuprofen that reduce prostaglandin formation by inhibiting cyclooxygenase ($COX1/COX2$) enzymes.

Vitamin K

A lipid-soluble vitamin that serves as a blood-clotting cofactor.

Vitamin A (Retinol)

A lipid-soluble hormone precursor and pigment involved in vision and signaling changes in gene expression.

Terpenes

A diverse family of compounds synthesized from isoprene units, often found in plant essential oils.